Proceedings World Geothermal Congress 2005 Antalya, Turkey, 24-29 April 2005 Colombian Geothermal Resources Claudia Alfaro*1, Francisco Velandia*2 and Héctor Cepeda*3 * INGEOMINAS. Dg. 53 No. 34-53. Bogotá, Colombia 1 [email protected] , 2 [email protected], 3 [email protected] Keywords: Colombia, Nevado del Ruiz, Paipa, Azufral, electromagnetic surveys and geochemistry of the aqueous structural geology of Paipa, vulcanism at the Eastern phase of the hot springs. From them a high temperature Cordillera, geochemistry of hot springs. geothermal system is proposed with a magmatic heat source, an upflow controlled by deep faults and a shallow ABSTRACT mixing process with a highly sodium sulfate mineralized water which “masks” the chemical composition of the deep During the last few years, new legal dispositions have reservoir fluid. favored the promotion of non-conventional energy sources in Colombia: The law 697 of 2001 declared the rational and efficient use of energy and the utilization of non- 1. INTRODUCTION conventional energy sources, as a social and public interest Between 2000 and 2005, new legal dispositions have matter as well as a national convenience issue. The same favored the promotion of non-conventional energy sources law, demands stimulus for developing non-conventional in Colombia. The law 697 of 2001 declared the rational and energy sources from the government. The edict 3683 dated efficient use of energy and the utilization of non- December 2003, regulates the promotion of non- conventional energy sources, as a social and public interest conventional energy sources, inside the frame of sustainable matter as well as a national convenience issue. The same development, following the recommendations of The law, demands encouragement for developing non- Johannesburg Summit, in which Colombia participated. conventional energy sources from the government. The edict 3683 dated December 19, 2003, regulates the Since 2000 the geothermal project of INGEOMINAS which promotion of non-conventional energy sources, inside the is the institution in charge of the geothermal exploration in frame of sustainable development, following the Colombia, have worked on two topics: 1) The inventory of recommendations of The Johannesburg Summit. hot springs, in two areas: Cerro Bravo – Cerro Machín Volcanic Complex and Cundinamarca Department and 2) INGEOMINAS is the governmental institution in charge of the first stage of exploration two areas: Azufral volcano the geothermal exploration in Colombia. During the last (Nariño Department) Paipa geothermal area (Boyacá five years this institution carried out studies of inventory of Department). hot springs at the geothermal areas of Cerro Bravo – Cerro Machín Volcanic Complex and Cundinamarca department The inventory of hot springs at Cerro Bravo – Cerro and the first stage of geothermal exploration at the Machín Volcanic Complex was based in the reinterpretation geothermal areas of Azufral Volcano and Paipa, which are of the geochemical existing information. The Santa Rosa de indicated in the Fig. 1. Cabal group, constituted by the springs of San Vicente and Santa Rosa sectors, revealed the highest interest as an 2. GEOTHERMAL STUDIES BACKGROUND energy resource given the highest geochemical temperatures inferred in the reservoir. This is proposed as The geothermal anomaly hosted in the Colombian territory an independent system from Nevado del Ruiz. related to the subduction zone is related in turn with several hydrothermal systems located mainly around the volcanoes The inventory of hot springs from Cundinamarca of the Andean Cordillera. The main identified geothermal department indicate the existence of this surface areas are the Cerro Bravo - Cerro Machín Volcanic manifestatons at 27 municipalities, from which 52 mineral Complex, the volcanoes from the south of the Country at and hot springs were characterized. The spatial distribution Nariño Department (Azufral, Chiles, Cumbal, Galeras of the springs shows a trend to increase their temperature volcanoes) and the Paipa – Iza sector, in Boyacá towards the East of the Department, reaching a maximum Department. A summary of the reconnaissance and of 73.6°C at Paratebueno locality. From the geochemistry prefeasibility studies, as well as the first version of the of the springs, Cundinamarca has geothermal resources of geothermal map was presented in the frame of the WGC low temperature related to a normal geothermal gradient. 2000 (Alfaro et al., 2000). The first stage of exploration at Azufral volcano included 3. UTILIZATION the preparation of the geological cartography of the area as The geothermal resources utilization is restricted in well as the updating of the chemical composition of hot Colombia to bathing and swimming with recreational springs. The stratigraphy of Quaternary deposits together purposes, mainly. However the local communities, where with a geochronological study allowed defining a new the hot springs are located, recognize their healing geological formation. The geochemistry of the springs properties. Currently, as result of the wide access to the shows a probable contribution of a saline non geothermal information, the development of the medical balneology source. The quartz geothermometers indicate a minimum and thermalism in many countries, particularly in Europe, is probable temperature of 180°C. object of an increasing interest in At Paipa geothermal area the work included geological studies of cartography, tectonics and volcanological, 1 Alfaro et al. and mud flows, product from the volcanic activity of the Quaternary. The Quaternary deposits from Cerro Bravo to Cerro Machín are predominantly andesitic rocks with variations from rhyodacites to dacites (Cerro Bravo, Nevado del Ruiz, Cerro Bravo – Cerro Machín Páramo de Santa Rosa and Machín) to basaltic andesites Volcanic complex from Nevado del Quindio and Nevado del Tolima, product Paipa geothermal of the Pleistocene and Holocene activity. area Cundinamarca The tectonic setting of the area is defined by the systems of Department faults Romeral, Palestina and Mulato with NNE-SSW Azufral volcano direction (Geocónsul, 1992). The Romeral fault, which divides the oceanic crust towards the west and, the continental crust to the east, represents and old subduction zone (Barrero et al., 1969, in Calvache & Monsalve, 1982). The compressive forces result in the uplift of the Cordillera Central and the formation of fault systems such as Mulato, Palestina, Marulanda, Salamina and Salento. Palestina fault has been an important conduct for the more ancient lava Figure 1. Location of the geothermal areas studied in emissions for the volcanoes of the Complex (CHEC et al., the last five year. Two types of studies were 1983). Local faults related to Romeral and Palestina, carried out: Inventory of hot springs identified at represent distensive strength due to the existence of dacitic blue areas and first stage of exploration activities dikes related to them. The current manifestation of these at red areas. faults is the volcanotectonic seismicity associated to the formation of fumarolic fields (Nereidas y La Olleta) and to Colombia, which is reflected in the creation of the the occurrence of hot springs (Calvache & Monsalve, Colombian Hydrothermal Techniques Association in 1998 1982). with the participation of the tourism sector as well as INGEOMINAS, as the governmental institution for 3.1.1.2 Hot Springs technical support, which after the recent reorganization From the spatial distribution and the probable association to keeps its mission of exploring the geothermal resources. specific volcanoes, the total of 100 springs, from which 74 Additionally, the agreement between the governments of can be considered thermal, were divided in nine (9) groups Rumania and Colombia was approved through the Law 595 presented in Fig. 2: (1) Cerro Bravo volcano, (2) Nevado of 2000, for the cooperation in tourism in particular to del Ruiz -eastern sector, (3) Batolito El Bosque, (4) Nevado promote the social tourism, health tourism, hydrothermal del Ruiz – western sector, (5) Santo Domingo, (6) Santa treatments, between others. The list of localities with hot Rosa, (7) El Bosque del Otún, (8) Nevado del Tolima and springs utilization in bathing and swimming is presented in (9) Cerro Machín volcano (Alfaro et al., 2002). Table 1, together with the estimation of the thermal energy utilization. In the localities of Paipa and Santa Rosa de A high diversity of chemical compositions is found in these Cabal, a more systematic use of these resources has been springs including those compatible with a significant implemented with programs for relaxation and health volcanic-magmatic fluid contribution (high temperature, tourism. high sulphate and chloride concentrations and very low pH), in the group 2. On the other hand, deep mature water 3. GEOTHERMAL RESOURCES AND POTENTIAL contribution is inferred, mainly, in the groups 1, 4, 6 and 9. In Colombia the geothermal resources are still an object of The group 1 located at the north of the Cerro Bravo volcano preliminary exploration and there are not significant is formed by 12 neutral bicarbonate springs around Cerro utilization developments. A description of exploration Bravo volcano. Their chemical composition indicates the studies carried out during the last five years is presented deep water contribution. The estimated reservoir next. temperature, based on the silica geothermometers points out 3.1 Inventory of Hot Springs up to 156°C.